The wear process results in generation of debris, or particles, of various size, shape, color distributions and chemical composition[1, 2, 3]. These distributions are dependent on normal load, sliding speed, environment and many other parameters[4]. The types of wear particles includes plate-shaped particles with aspect ratios of 2-10 produced as a result of accumulated plastic deformations, ribbon-shaped with aspect ratios higher than 10, produced by abrasion and even spherical particles[1]. Formation of spherical particles is not well understood, as they can be found in different types of contacts[5] and combinations of materials[6].

It is believed that the wear debris reflects the wear mechanism of its formation[7, 8]. Reda et al. [9] experimentally studied formation of debris in lubricated sliding steel contacts, and distinguished 6 wear regimes based on characteristic wear particles morphology and composition.